71 million years ago. Hope it helps :)
Answer:
D. They force Africa to lower the prices on its goods.
Explanation:
Trade barriers refers to the restrictions on the international trade and commerce that is induced by the government of a country. Trade barriers have a bad effect on the economy of a country. It is detrimental as considered by economist.
Countries like that of Africa who imposed a trade barrier on the international trade suffers a lot on economic efficiency of the country. These countries depends on the exports for funding their economy. Trade barriers in Africa forced the businesses to sell their goods at a lower price that affects the economy greatly.
The Congo and Niger rivers have interesting irregular courses, and instead of going just in a certain direction, they circle around big areas. This is due to the shape of the landscape, and also because of the types of rocks in the surrounding areas where these two rivers flow.
The shape of the landscape is crucial in the course of a river, since every river is moving through the lowest parts where there isn't obstacles, so these rivers have followed that pattern and it turned out to give them irregular course. Also, the types of rocks on their way are very important, so these rivers managed to get through the sediment rocks as they are easy to erode, but haven't been able to break through the igneous rocks that are much harder.